Bone dowel cutter

ABSTRACT

A device is provided for cutting dowels from a bone mass which is easily disassembled for cleaning and sterilization. The dowel cutter includes an axial mounting member having a proximal end portion configured for engagement with a drill chuck and a distal end portion configured to receive a cylindrical cutting blade, an elongated supporting shaft having a distal end portion configured to support a drill guide, and a securement mechanism formed integral with the mounting member for releasably maintaining the relative orientation of the supporting shaft and the axial mounting member during utilization.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a device for cutting bone, and moreparticularly, to an apparatus for cutting dowels from a bone mass.

2. Description of the Related Art

Many osteopathic surgical procedures employ plugs or dowels cut frombone as protheses. Devices for cutting and forming plugs or dowels frombone are known in the art and include both hand-held andplatform-mounted configurations. An example of a platform-mounted deviceis disclosed in U.S. Pat. No. 4,416,278 to Miller which includes a diecarried on a plunger that is housed in a sleeve. A pivoting handle whichtakes the form of a lever is connected to the plunger to effect themovement thereof relative to the sleeve.

Another apparatus for forming bone plugs which has a platform-mountedconfiguration is disclosed in U.S. Pat. No. 4,559,936 to Hill. Thisdevice has a cup-like fixture for supporting the bone from which theplug is cut, and includes a cylindrical cutting tool which rotatesaxially and translates longitudinally with respect to the bonesupporting fixture during a plug forming procedure.

An example of a hand-held apparatus for removing a core from a bone massis disclosed in U.S. Pat. No. 4,649,918 to Pegget et al. and includes acylindrical member having a honed cutting edge which is axially rotatedto cut the bone core. A similar device is disclosed in U.S. Pat. No.4,798,213 to Doppelt which is configured to obtain a bone biopsyspecimen. The device includes an introducer, a trocar, a manuallyoperated cylindrical cutting drill, and a plunger for removing the bonespecimen from the drill.

Another prior art device utilized to cut dowels from bone ismanufactured by Cloward™ and is configured to be mounted to aconventional hand-held surgical drill. The Cloward™ device isillustrated in FIGS. 1-4 of the subject application and is described indetail hereinbelow.

As will be discussed, the complex construction of the Cloward™ deviceencumbers its disassembly, and it is therefore difficult to clean andsterilize after use. It would be beneficial to provide a dowel cutterfor use with a powered surgical drill that can be easily disassembledfor cleaning. The subject invention describes such a device.

SUMMARY OF THE INVENTION

The subject invention is directed to a device for cutting and formingdowels from a bone mass for subsequent use as prostheses duringosteopathic surgical procedures. The device is configured for use with apowered drill which includes an elongated barrel section having a chuckprovided at a distal end thereof. In a preferred embodiment of thesubject invention, the dowel cutting assembly includes an axial mountingmember having a proximal end portion configured for engagement with thechuck, and a distal end portion configured to receive a cylindricalcutting blade. An elongated supporting shaft having a distal end portionconfigured to support a drill guide pin is mounted for coaxial movementwith respect to the axial mounting member, and means are provided whichare integral with the mounting member for releasably maintaining therelative orientation of the supporting shaft and the axial mountingmember.

In one embodiment of the subject invention, a dowel cutting assembly isprovided which is particularly adapted for use with a cannulated drillthat has an elongated axial bore extending through the barrel sectionthereof. In such an embodiment, the elongated supporting shaft of thedowel cutting assembly is configured to extend through the axial bore ofthe drill and has a plunger provided at the proximal end thereof forfacilitating axial movement of the supporting shaft. In anotherembodiment of the subject invention, the supporting shaft is springbiased in a distal direction and threaded means are integrallyassociated with the mounting member for engaging the supporting shaft toreleasably maintain the relative orientation thereof with respect to theaxial mounting member. In yet another embodiment of the subjectinvention, the elongated supporting shaft has a transverse flange formedat a proximal end thereof and a transverse slot is formed in a distalportion of the mounting member for releasably engaging the flange tomaintain the relative orientation of the supporting shaft and the axialmounting member.

These and other features of the bone dowel cutter of the subjectinvention will become more readily apparent from the following detaileddescription of the invention taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that one skilled in the art to which the subject invention appertainswill better understand how to make and use the bone dowel cutter of thesubject invention, preferred embodiments thereof, as well as anembodiment of a prior art device, will be described hereinbelow withreference to the drawings wherein:

FIG. 1 is a perspective view of a prior art dowel cutting assembly shownin conjunction with a conventional powered surgical drill, aconventional cylindrical cutting blade, and a conventional drill guide;

FIG. 2 is a side elevational view of the prior art dowel cuttingassembly illustrated in FIG. 1 with the drill guide shaft locked in adistal position and the drill guide penetrating into a bone mass;

FIG. 3 is a side elevational view of the prior art dowel cuttingassembly illustrated in FIG. 1 with the drill guide shaft in afree-movement position and the cylindrical cutting blade penetratinginto the bone mass;

FIG. 4 is a side elevational view of the prior art dowel cuttingassembly illustrated in FIG. 1 after the cutting blade has formed adowel from the bone mass and the drill guide shaft has moved to aproximal position;

FIG. 5 is a side elevational view in partial cross-section of a firstembodiment of a dowel cutting assembly constructed in accordance withthe subject invention and adapted for utilization with a conventionalcannulated powered surgical drill;

FIG. 6 is a side elevational view, with parts separated for ease ofillustration, of a second embodiment of a dowel cutting assemblyconstructed in accordance with the subject invention and adapted forutilization with a conventional powered surgical drill;

FIG. 7 is a side elevational view of a third embodiment of a dowelcutting assembly constructed in accordance with the subject inventionand adapted for utilization with a conventional surgical drill;

FIG. 8 is a perspective view of the dowel cutting assembly illustratedin FIG. 5 shown in conjunction with a conventional cannulated poweredsurgical drill, a conventional cylindrical cutting blade, and aconventional drill guide;

FIG. 9 is a side elevational view in partial cross-section of the dowelcutting assembly illustrated in FIG. 5 with the drill guide shaft lockedin a distal position and the drill guide penetrating into a bone mass;

FIG. 10 is a side elevational view in partial cross-section of the dowelcutting assembly illustrated in FIG. 5 with the drill guide shaft in afree-movement position and the cylindrical cutting blade penetratinginto the bone mass;

FIG. 11 is a side elevational view in partial cross-section of the dowelcutting assembly illustrated in FIG. 5 after the cutting blade hasformed a dowel from the bone mass and the drill guide shaft has moved toa proximal position;

FIG. 12 is a side elevational view in partial cross-section of the dowelcutting assembly illustrated in FIG. 5 upon removal of the formed bonedowel from the bone mass;

FIG. 13 is a perspective view of the dowel cutting assembly illustratedin FIG. 5 with the drill guide shaft advanced distally to expel theformed bone dowel from the cylindrical cutting blade;

FIG. 14 is a perspective view of the dowel cutting assembly illustratedin FIG. 6 shown in conjunction with a conventional powered surgicaldrill, a conventional cylindrical cutting blade, and a conventionaldrill guide;

FIG. 15 is a side elevational view in partial cross-section of the dowelcutting assembly illustrated in FIG. 6 with the drill guide shaft in alocked position and the drill guide penetrating into a bone mass;

FIG. 16 is a side elevational view in partial cross-section of the dowelcutting assembly illustrated in FIG. 6 with the drill guide shaft andthe cylindrical cutting blade penetrating into the bone mass;

FIG. 17 is a side elevational view in partial cross-section of the priordowel cutting assembly illustrated in FIG. 6 as the drill guide shaft isremoved from the cutting assembly prior to formation of the dowel fromthe bone mass;

FIG. 18 is a side elevation view in partial cross-section of the dowelcutting assembly illustrated in FIG. 6 after the cylindrical cuttingblade has formed the bone dowel from the bone mass;

FIG. 19 is a perspective view of the dowel cutting assembly illustratedin FIG. 7, with parts separated for ease of illustration, in conjunctionwith a conventional powered surgical drill, a conventional cylindricalcutting blade, and a conventional drill guide;

FIG. 20 is a side elevational view in partial cross-section of the dowelcutting assembly illustrated in FIG. 7 with the spring biased drillguide shaft locked in a distal position and the drill guide penetratinginto a bone mass;

FIG. 21 is a side elevational view in partial cross-section of the dowelcutting assembly illustrated in FIG. 7 with the spring biased drillguide shaft in a free-movement position and the cylindrical cuttingblade penetrating into the bone mass;

FIG. 22 is a side elevational view in partial cross-section of the dowelcutting assembly illustrated in FIG. 7 after the cutting blade hasformed a dowel from the bone mass and the spring biased drill guideshaft has retracted and moved to a proximal position; and

FIG. 23 is a side elevational view in partial cross-section of the dowelcutting assembly illustrated in FIG. 7 upon removal of the formed bonedowel from the bone mass with the spring biased drill guide shaftdisposed in a distal position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the drawings and in the description which follows, the term"proximal" as is traditional, will refer to the end of the dowel cuttingassembly which is closest to the user, while the term "distal" willrefer to the end of the assembly which is furthest from the user.

Referring now to the drawings, there is illustrated in FIG. 1, a priorart dowel cutting device which is designated generally by referencenumeral 10. Dowel cutter 10 is distributed by Codman and Shurtleff,Inc., Randolph, Mass. 02368 (as well as others), under the Cloward™, andis adapted for use with a conventional surgical drill identified byreference numeral 20. Surgical drill 20 has an elongated barrel portion22 and a depending handle portion 24 with a trigger 26 for actuating thedrill. A chuck assembly 28 is provided at the distal end of barrelportion 22 for receiving and coupling with the proximal end of dowelcutter 10.

The prior art dowel cutter 10 includes an inner mounting shaft 30 havinga proximally extending connector 32 configured for reception in chuckassembly 28 and further defining an elongated shaft body 34 having aninterior bore 36 opening through the periphery and the distal end of theshaft body. A threaded area 38 is defined at the distal end of shaftbody 34 for receiving a conventional cylindrical cutting blade which isidentified by reference numeral 40. Dowel cutter 10 further includes aninternal support shaft 42 slidably supported within interior bore 36 andhaving a distal end configured to threadably receive a conventionaldrill guide member 44. An outer sleeve 46 encloses the shaft body 34 andis axially movable with respect thereto. A slide-bolt arrangement isprovided for maintaining the relative orientation of the internalsupport shaft 42, shaft body 34, and the outer sleeve 46 duringutilization. It includes a flange 48 which extends radially outwardlyfrom a proximal end of support shaft 42 and a coved slot 50 havingdistal and proximal retention areas 50a and 50b for receiving flange 48.

Turning to FIGS. 2-4, the prior art Cloward™ device is shown during adowel forming procedure. As illustrated in FIG. 2, drill guide member 44is extended beyond the distal end of cutting blade 40 to engage bonemass "B" and provide a pilot hole for cutting blade 40. Drill guidemember 44 is maintained in this extended position through the engagementof flange 48 in distal retention area 50a. At such a time, a knurledfitting 52, which is threadably positioned on shaft body 34 adjacent theproximal end thereof, is advanced distally to impinge upon the proximalend of outer sleeve 46 and urge it distally against the proximal end ofcutting blade 40, thereby further securing the position of flange 48 inretention area 50a.

After the pilot hole has been formed by drill guide member 44, flange 48is manually released from retention area 50a, and support shaft 42 ispermitted to retract proximally, as shown in FIG. 3, to enable thedistal edge of cutting blade 40 to engage bone mass "B". Finally, asillustrated in FIG. 4, when cutting blade 40 is fully extended into bonemass "B", support shaft 42 is fully retracted such that flange 48 isadjacent proximal retention area 50b. At such a time, the flange may beengaged within the proximal retention area and the cutting blade may bewithdrawn from the bone mass. After use, because of the complex coaxialconstruction of the Cloward™ device, disassembly to facilitateefficacious cleaning and sterilization is encumbered by the complexityof the device.

Referring now to FIGS. 5-7, there is illustrated three dowel cuttingassemblies constructed in accordance with a preferred embodiment of thesubject invention. The first dowel cutting assembly is illustrated inFIG. 5 and is designated generally by reference numeral 100. As will bediscussed in detail hereinbelow, dowel cutter 100 is particularlyadapted for use with a cannulated surgical drill of the type illustratedin FIG. 8. The second and third dowel cutting assemblies, which areillustrated in FIGS. 6 and 7 and designated generally by referencenumerals 200 and 300, respectively, are adapted for use with anon-cannulated surgical drill, such as surgical drill 10 describedearlier with respect to the prior art Cloward™ device. As will bediscussed in detail hereinbelow, each of the three dowel cutters of thesubject invention are easily disassembled after use, and therefore, theymay be cleaned and sterilized more efficaciously than the prior artCloward™ device.

Referring now to FIG. 8, dowel cutter 100 is illustrated in conjunctionwith a cannulated surgical drill 20' having an axial bore 22a extendingthrough the barrel portion 22' thereof, a conventional cylindricalcutting blade 40, and a conventional drill guide member 44. Dowel cutter100 includes an axial mounting member 110 having a medial body portion112 from which extends a proximal coupling 114 and a distal threadedstem 116. The proximal coupling 114 is configured for reception withinthe chuck assembly 28' of cannulated drill 20', and the threaded stem116 is configured to receive cutting blade 40.

Dowel cutter 100 further includes an elongated support shaft 120configured to extend through axial bore 22a of the barrel portion 22' ofcannulated drill 20'. A plunger 122 is provided at the proximal end ofsupport shaft 120 for facilitating user manipulation of the shaft, andthe distal end of support shaft 120 is threaded to mount a fixture 124adapted to threadably receive drill guide member 44. A threaded fitting130 is operatively associated with the medial body portion 112 of axialmounting member 110. Fitting 130 extends transversely through bodyportion 112 into the axial pathway 125 (FIG. 9) that extendslongitudinally therethrough, to interact with support shaft 120 andselectively maintain the longitudinal and axial orientation thereof withrespect to axial mounting member 110.

Turning now to FIGS. 9-13, there is illustrated, in sequential order,the method of utilizing dowel cutter 100 to cut and form a dowel "D"from a bone mass "B". Initially, as illustrated in FIG. 9, with threadedfitting 130 engaged against support shaft 120, drill guide member 44 isdriven into bone mass "B" to form a pilot hole and properly guide thedistal cutting edge of blade 40 into the bone mass. As shown in FIG. 10,once the honed cutting edge of blade 40 has penetrated the bone mass,fitting 130 is released, liberating support shaft 120, and permitting itto slidably retract proximally as the dowel is formed. Support shaft 120continues to translate proximally until the dowel "D" is fully formed,as illustrated in FIG. 11. Thereafter, cutting blade 40 is withdrawnfrom bone mass "B" with the formed dowel "D" disposed therein. To removedowel "D" from cutting blade 40, support shaft 120 is advanced distally,ejecting the formed dowel from the cutting blade.

Following the dowel cutting procedure, cutting blade 40 is removed frommounting member 110 and guide member 44 is removed from fixture 124.Then, the fixture itself is removed from the distal end of support shaft120 and the support shaft is removed from the axial bore 22a defined inthe barrel portion 22' of surgical drill 20'. Subsequently, the proximalcoupling 114 is released from drill chuck 28', and thereupon dowelcutting assembly 100 is completely disassembled for cleaning andsterilization.

Referring to FIG. 14, dowel cutter 200 is illustrated in conjunctionwith a conventional surgical drill 20 having a barrel portion 22 with achuck assembly 28 provided at the distal end thereof, a cutting blade40, and a drill guide 44. Dowel cutter 200 includes an axial mountingmember 210 having a medial body portion 212 from which extends proximalcoupling 214 configured for reception in chuck assembly 28, and a distalthreaded stem 216 configured to receive cutting blade 40.

Dowel cutter 200 further includes an elongate support shaft 220 having athreaded bore 225 extending partially therethrough from a distal endthereof to receive and mount drill guide 44. The proximal end of supportshaft 220 is formed with a transverse flange 222 from which extends acylindrical stem 224. Flange 222 and stem 224 are dimensioned andconfigured to engage complementary transverse slot 226 and axial bore228 defined in mounting member 210. The engagement of thesecomplementary structures maintains the relative axial orientation ofsupport shaft 220 and mounting member 210 during utilization.

Referring now to FIGS. 15-18, there is illustrated, in sequential order,the method by which dowel cutter 200 is utilized to form and cut a dowelfrom a bone mass "B". Initially, with flange 222 and slot 226 engaged tomaintain the relative axial orientation of support shaft 220 andmounting member 210, drill guide 44 is driven into bone mass "B", toguide the distal edge of cutting blade 40 toward the bone mass, asillustrated in FIG. 15. As shown in FIG. 16, the complementarystructures remain engaged until the distal edge of cutting blade 40 haspenetrated the bone mass. Then, as illustrated in FIG. 17, dowel cutter200 is withdrawn from the bone mass, and support shaft 220 is disengagedfrom mounting member 210 and displaced from the assembly. At such atime, the cutting blade is directed back to the bone mass, and the dowel"D" is formed thereby, as shown in FIG. 18. At the conclusion of thedowel forming procedure, cutting blade 40 is removed from the distalthreaded stem 216 of mounting member 210 and the proximal coupling 214is released from drill chuck 28. Finally, drill guide 44 is detachedfrom the distal end of support shaft 220 and the disassembled dowelcutter can be efficaciously cleaned and sterilized for subsequentutilization.

Referring to FIG. 19, dowel cutter 300 is illustrated in conjunctionwith drill 20, cutting blade 40, and drill guide member 44. Dowel cutter300 includes an axial mounting member 310 having an elongate bodyportion 312 from which extends a proximal coupling 314 and a distalthreaded stem 316. Coupling 314 is configured for reception in drillchuck 28 and stem 316 is configured to receive cutting blade 40. Inaddition, a stepped axial bore 315 extends through mounting member 310,decreasing in diameter within the proximal coupling 314, to accommodatesupport shaft assembly 320.

In this third configuration of the subject invention, support shaft 320is spring biased in a distal direction to facilitate automatic ejectionof a formed dowel from cutting blade 40 at the conclusion of a dowelforming procedure. Support shaft assembly 320 has a piston-likeconstruction including an elongate inner rod member 322 and a coaxialouter plunger sleeve 324. A guide pin 326 extends radially outward fromrod member 322 and is engaged within an elongate slot 328 formed inplunger sleeve 324 (see FIG. 22). Pin 326 and slot 328 limit therelative movement of plunger sleeve 324 with respect to rod member 322.Support shaft assembly 320 further includes a coiled compression spring330 which is retained at its proximal end to plunger sleeve 324. Acompression fitting 332 is threadably mounted to the distal end of rodmember 322 and has a proximal stem 334 for retaining the distal end ofcompression spring 330. Fitting 332 also has a threaded bore 336 forreceiving drill guide member 44. When dowel cutter 300 is assembled withsupport shaft assembly 320 disposed within axial mounting member 310,the proximal end of plunger sleeve 324 abuts against an internal wall325 of stepped axial bore 315 (see FIG. 20).

Dowel cutter 300 further includes a threaded fitting 340 which isoperatively associated with the elongate body portion 312 of axialmounting member 310. Fitting 340 extends transversely through bodyportion 312 into the distal section of axial bore 315 to interact with aproximal portion of rod member 322 and selectively maintain thelongitudinal and axial orientation thereof with respect to axialmounting member 310.

Turning now to FIGS. 20-23, there is illustrated, in sequential order, amethod of forming a bone dowel utilizing dowel cutter 300. First, asillustrated in FIG. 20, fitting 340 is tightened to engage rod member322 and maintain drill guide member 44 in a distal position, extendingfrom cutting blade 40. In this position, coiled spring 330 is in arelaxed, decompressed state. Then, as shown in FIG. 21, after drillguide 44 has penetrated into bone mass "B" and guided the honed edge ofcutting blade 40 into the bone mass, threaded fitting 340 is released,thereby liberating rod member 322 to permit proximal retraction of guidemember 44 against the bias of coiled spring 330.

When dowel "D" has been fully formed, and rod member 322 is in itsproximal-most position, coiled spring 330 will be fully compressed.Then, as shown in FIG. 22, fitting 340 is once again tightened to engagerod member 322, and maintain the longitudinal orientation thereof withrespect to mounting member 310. Once cutting blade 40 has been withdrawnfrom bone mass "B", fitting 340 is released, and compression spring 300urges rod member 322 distally, ejecting the formed dowel "D" fromcutting blade 40.

Following the dowel forming procedure, dowel cutter 300 is easilydisassembled by removing support shaft 320 from axial mounting member320. The compression fitting 332 is then removed from the distal end ofrod member 322, and the proximal end of spring 330 is released fromplunger sleeve 324. At such a time, each part of dowel cutter 300 can beeffectively cleaned and sterilized for subsequent utilization.

Although the subject invention has been described with respect topreferred embodiments, it will be readily apparent to those havingordinary skill in the art to which it appertains that changes andmodifications may be made thereto without departing from the spirit orscope of the subject invention as defined by the appended claims.

What is claimed is:
 1. A dowel cutting assembly for use with a powereddrill which includes an elongated barrel section having a chuck providedat a distal end thereof, comprising:a) an axial mounting member having aproximal end portion configured for engagement with the chuck and adistal end portion configured to receive a cylindrical cutting blade; b)an elongated supporting shaft having a distal end portion configured tosupport a drill guide, said supporting shaft mounted for coaxialmovement with respect to said axial mounting member; and c) securementmeans integral with said mounting member for releasably maintaining therelative longitudinal orientation of said supporting shaft and saidaxial mounting member.
 2. A dowel cutting assembly as recited in claim1, wherein an axial bore extends at least partially through said axialmounting member to accommodate said elongated supporting shaft.
 3. Adowel cutting assembly as recited in claim 2, wherein said securementmeans includes a threaded fastener mounted in said axial mounting memberand extending transversely therethrough to said axial bore to releasablyengage said elongated supporting shaft.
 4. A dowel cutting assembly asrecited in claim 1, wherein said elongated supporting shaft is springbiased in a distal direction with respect to said axial mounting member.5. A dowel cutting assembly as recited in claim 4, wherein saidelongated supporting shaft includes an elongate support rod, a sleevemovably supported on said support rod, and a coiled compression springmounted to said sleeve.
 6. A dowel cutting assembly as recited in claim1, wherein a mounting fixture is mounted on the distal end portion ofsaid supporting shaft for detachably supporting a drill guide.
 7. Adowel cutting assembly as recited in claim 1, wherein a threaded stemextends distally from said axial mounting member for threadablyreceiving a cylindrical cutting blade.
 8. A dowel cutting assembly asrecited in claim 7, wherein a transverse slot is formed in said threadedstem and a transverse flange extends from a proximal end of saidsupporting shaft which is dimensioned and configured to engage saidtransverse slot.
 9. A dowel cutting assembly for use with a powereddrill which includes an elongated barrel section having a chuck providedat a distal end thereof and an axial bore extending therethrough,comprising:a) an axial mounting member having a proximal end portionconfigured for engagement with the chuck and a distal end portionconfigured to receive a cylindrical cutting blade; b) an elongatedsupporting shaft configured to extend through the axial bore of thedrill and having a distal end portion configured to support a drillguide, said supporting shaft mounted for coaxial movement with respectto said axial mounting member; and c) threaded means integral with saidmounting member for engaging said supporting shaft to releasablymaintain the relative longitudinal orientation of said supporting shaftand said axial mounting member.
 10. A dowel cutting assembly as recitedin claim 9, wherein an axial bore extends through said axial mountingmember to accommodate said elongated supporting shaft.
 11. A dowelcutting assembly as recited in claim 10, wherein a plunger is providedat a proximal end of said elongated supporting shaft to facilitate saidcoaxial movement of said supporting shaft.
 12. A dowel cutting assemblyas recited in claim 10, wherein said threaded means includes a threadedfastener mounted in said axial mounting member and extendingtransversely therethrough to said axial bore to releasably engage saidelongated supporting shaft.
 13. A dowel cutting assembly as recited inclaim 9, wherein a mounting fixture is mounted on the distal end portionof said supporting shaft for detachably supporting the drill guide. 14.A dowel cutting assembly as recited in claim 9, wherein a threaded stemextends distally from said axial mounting member for threadablyreceiving the cylindrical cutting blade.
 15. A dowel cutting assembly asrecited in claim 4, wherein said elongated supporting shaft includes anelongate support rod, a sleeve movably supported on said support rod,and a coiled compression spring mounted to said sleeve.